Artificial retina device with stimulating and ground return electrodes disposed on opposite sides of the neuroretina and method of attachment

ABSTRACT

An artificial retina device to electrically stimulate a neuroretina of an eye to produce artificial vision, the artificial retina device comprising: an electrical source; at least one stimulating electrode connected with the electrical source; and at least one ground return electrode connected with the electrical source, wherein the stimulating electrode and ground return electrode are configured to be disposed within the eye on opposite sides of the neuroretina.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/293,871, filed Dec. 2, 2005, which is a continuation of U.S.application Ser. No. 10/142,277, filed May 9, 2002, now U.S. Pat. No.7,003,354, issued Feb. 21, 2006, which is a continuation of U.S.application Ser. No. 09/564,841, filed May 4, 2000, now U.S. Pat. No.6,427,087, issued Jul. 30, 2002, which prior applications are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention is generally directed to medical devices. Moreparticularly, the present invention is directed to an artificial retinamedical device and method to more efficiently stimulate electrically andwith higher resolution, neuroretinal cells in partially damaged retinasto produce artificial vision. The invention provides improved efficiencyand resolution of the device by using transretinal electrical currentstimulation provided by stimulation and ground return electrodes thatare disposed on opposite sides of the neuroretina.

BACKGROUND Background and Relevant Art

A variety of retina diseases cause vision loss or blindness bydestruction of the vascular layers of the eye that include the choroidand choriocapillaris, and the outer retinal layers that include Bruch'smembrane and retinal pigment epithelium. Loss of these layers is oftenaccompanied by degeneration of the outer portion of the neuroretina,typically the photo-receptor layer. Variable sparing may occur of theremaining neuroretina composed of the outer nuclear, outer plexiform,inner nuclear, inner plexiform, ganglion cell and nerve fiber layers.

Known prior efforts to produce vision by retinal electrical stimulationused arrays of stimulating electrodes with their ground return electrodeor electrodes disposed either entirely on the epiretinal or thesubretinal side of the neuroretina. Placement of stimulating and groundreturn electrodes together in this fashion resulted in inefficientstimulation of the neuroretina because the electrical field was notforced directly through the neuroretina. Resolution was also degradedbecause of diffuse spreading of each stimulating electrode's electricalfield.

BRIEF SUMMARY

The artificial retina device of this invention is preferably composed oftwo basic units, the stimulating electrode unit and the ground returnelectrode unit. In one embodiment, the two units are physically andelectrically continuous, or physically and electrically connected by aninsulated tail-like conductor that in some embodiments supports,positions, and aligns the two units on opposite sides of the neuroretinarelative to each other. The stimulating electrode unit is, for example,a silicon disk 3 mm in diameter and 25 microns thick, and is comprisedof separated stimulating microelectrode subunits. Preferably, thestimulating electrode unit has a ground return electrode unit extendingfrom one edge, comprised of a silicon tail with an insulated conductorleading to the ground return electrode at its tip. The stimulatingmicroelectrode subunits of the stimulating electrode units delivercurrent generated by one or more microphotodiodes connected, forexample, in series and fabricated within the subunit. The preferrednumber of microphotodiodes per subunit is one.

In some embodiments, the stimulating electrode and ground returnelectrode are configured to be disposed on opposite sides of theneuroretina. For example, in some embodiments, the ground returnelectrode is disposed on the outside of an eye. In other embodiments,the ground return electrode is disposed on a scelra surface outside ofan eye. In further embodiment, an electrical source is connected withthe stimulating electrode, the ground return electrode, or both.

In other embodiments, each microelectrode subunit is preferablyfabricated on a node of a disk-shaped silicon web, the subunitsseparated by open areas of the web. The open areas of the web allownourishment and oxygen from the outer retinal circulation to diffuseinto the neuroretina.

In the preferred embodiment, on the backside of the stimulatingelectrode unit, i.e. the side opposite the incident light side, aninsulated common conductor is constructed and arranged to electricallyground the microelectrode subunits. The common ground conductorpreferably continues along the length of the ground return electrodeunit and terminates in an exposed ground return electrode at or near thetip of the ground return electrode unit, and disposed in the vitreouscavity. The exposed ground return electrode tip in the vitreous cavityallows the electrical field generated by the microelectrode subunits inthe subretinal space to transretinally stimulate the neuroretina.

In a second embodiment, an additional tail with an embedded conductorand an electrode tip is connected to the ground electrode tip of theground electrode unit to extend the location of the ground electrodefurther into the vitreous cavity.

In a third embodiment, the conductor of the ground electrode unit iselectrically connected with an additional bias photodiode or photodiodesto increase the voltage and current generated by the device. In thislatter case, the ground electrode of the device is preferably disposedon the additional bias photodiode or photodiodes disposed in thevitreous cavity.

In a fourth embodiment, the bias photodiode or photodiodes are placed inthe lens capsular bag of the eye after surgical removal of the lensnucleus and cortical material.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent to thoseskilled in the art with reference to the detailed description and thedrawings, of which:

FIG. 1A is a plan view of a preferred embodiment showing the stimulatingelectrode unit and the ground return electrode unit.

FIG. 1B is a side view of FIG. 1A showing the stimulating electrode unitand the ground return electrode unit.

FIG. 2A is a plan view of the tail extension of the preferredembodiments, that physically and electrically couples to the groundreturn electrode unit of FIGS. 1A and 1B to extend the location of theground return electrode further into the vitreous cavity of the eye.

FIG. 2B is a cross-sectional view of the tail extension of the preferredembodiments.

FIG. 3 is a perspective view showing the tail extension of FIGS. 2A and2B attached to the ground return electrode unit of FIGS. 1A and 1B.

FIG. 4 is a perspective view of another embodiment, showing thestimulating electrode unit fabricated as a circular silicon web to allownourishment to flow between the choroid and the neuroretina, and thestimulating electrode subunits fabricated at the intersecting nodes ofthe web.

FIGS. 4A and 4B are magnified plan and sectional views respectively ofthe embodiment of FIG. 4 where the stimulating electrode subunits of thestimulating electrode unit are each comprised of three microphotodiodeselectrically connected in series to increase the voltage output of eachstimulating electrode subunit.

FIG. 5 is a cross-sectional view of FIGS. 1A and 1B, in the eye with astimulating electrode unit in the subretinal space and a ground returnelectrode of the ground return electrode unit exposed in the vitreouscavity.

FIG. 6 is a cross-sectional view of the device of FIG. 5 with theattached tail extension of FIGS. 2A and 2B.

FIG. 7 is a cross-sectional view of another embodiment, showing thedevice of FIGS. 1A and 1B with an electrode stimulating unit implantedin the subretinal space and a ground return electrode loop of the groundreturn electrode unit disposed in the vitreous cavity.

FIG. 8 is a cross-sectional view of another preferred embodiment,showing the device of FIGS. 1A and 1B with a stimulating electrode unitimplanted in the subretinal space and a tail extension electricallyconnecting to a bias photodiode disposed in the lens capsule of the eye,the bias photodiode containing the extended location of the groundreturn electrode, and the bias photodiode providing additional voltageand/or current to the electrode stimulating unit in the subretinalspace.

FIG. 9 is a cross-sectional view of another embodiment, showing thedevice of FIGS. 1A and 1B with its stimulating electrode unit implantedin the subretinal space and a tail extension electrically connecting toa bias photodiode disposed in front of the iris, in the anterior chamberof the eye, the bias photodiode containing the extended location of theground return electrode, and the bias photodiode providing additionalvoltage and/or current to the electrode stimulating unit in thesubretinal space.

DETAILED DESCRIPTION

Referring to the drawings, as shown in FIGS. 1A and 1B, the preferredembodiment of retinal device 10 has a stimulating electrode unit 12 anda curved ground return electrode unit 16 configured for implantationinto an eye such that the retinal device may be positioned completelyinside the eye and stimulate opposite or substantially opposite sides ofthe neuroretina. The two components 12 and 16 are preferably physicallyfabricated on a single thin silicon chip substrate 11, but may befabricated separately and then joined together. The stimulatingelectrode unit 12 includes an array of stimulating electrode subunits 22each composed of one or more electrical sources such as a photodetectoror photodetectors. In a preferred embodiment, the photodetectors may beimplemented as microphotodiodes 23 a electrically connected, forexample, in series.

A stimulating electrode 23 b contacts at least one of individual cells,groups of cells, portions of cells and nerve fibers of the neuroretina.The ground return electrode 14 is preferably disposed at or near the tipof the ground return electrode unit 16. The stimulating electrode 23 band ground return electrode 14 are disposed on opposite sides of aneuroretina, or if the neuroretina is partially missing or damaged, thenon opposite sides of the remainder of the neuroretina. In a preferredembodiment, the stimulating electrode 23 b is disposed in a subretinalspace of the neuroretina and the ground return electrode 14 is disposedon an epiretinal side of the neuroretina. In another embodiment, thepositions are reversed, with the ground return electrode 14 beingdisposed in the subretinal space of the neuroretina and the stimulatingelectrode 23 b being disposed on the epiretinal side of the neuroretina.

Also as shown in FIGS. 1A and 1B, exemplary components of the preferredembodiment of retinal device 10 includes the thin silicon substrate 11,stimulating electrode unit 12, stimulating electrode subunits 22,microphotodiodes 23 a electrically connected, for example, in series,within stimulating electrode subunits 22 and an iridium/iridium oxidestimulating electrode 23 b of stimulating electrode subunits 22. Themicrophotodiodes 23 a or other electrical source preferably providesstimulation to the neuroretina from the subretinal and vitreous cavitysides of the eye. Alternatively, the electrical source could providestimulation from outside the eye in response to incident light. Forexample, the electrical source could send signals proportional to sensedincident light via hardwiring into the subretinal space and vitreouscavity of the eye. In another embodiment, the electrical source couldtransmit a signal in a wireless fashion to the eye using, for example,radio frequency (rf) to send signals to a coil located in the eye thatis in communication with the stimulation and ground electrodes. Otherknown mechanisms may also be used for providing electrical energy to theeye in response to incident light.

Also included with the ground return electrode unit 16 is a siliconnitrite stress layer 17 that preferably shapes the ground returnelectrode unit 16 in a generally curved shape to direct the groundreturn electrode unit 16 into the vitreous cavity. Although a curvedirects the ground electrode unit 16 into the vitreous cavity, othershapes could be used, such as an angled ground electrode, to perform thesame function, but may be more difficult to fabricate. The ground returnelectrode 14 is preferably produced of an iridium/iridium oxide andincludes a titanium adhesion layer 14 a and a p+ tub 14 b disposed undera titanium adhesion layer 14 a to allow electrical contact with thedoped silicon substrate 11. The retinal device 10 also preferablyincludes a silicon dioxide layer 15 that insulates the stimulatingelectrode unit 12 and ground return electrode unit 16.

As shown in FIGS. 1A and 1B, the stimulating electrode unit 12 includesa plurality of stimulation electrode subunits 22 having one or moremicrophotodiodes 23 a electrically connected, for example, in serieswithin each electrode subunit 22. The preferred number ofmicrophotodiodes 23 a is one unit per microelectrode subunit 22. Thelayers of the microphotodiode are, for example, from the incident lightsurface, the iridium/iridium oxide electrode 23 b, titanium adhesionlayer 23 c, n+ tub 23 d, intrinsic layer 23 e and the silicon substrate11. Those skilled in the art will appreciate that other arrangementscould be used where the microelectrode subunits are subunits capable ofgenerating electrical current.

Also shown in FIGS. 1A and 1B, the ground return electrode unit 16preferably includes a positioning hole 24 that allows the retinal device10 to be positioned with instruments during surgery. The ground returnelectrode unit 16 in another embodiment includes notches 26 that allow asecure fit for attachments that have corresponding protrusions that fitinto the notches 26, as described in more detail below.

As shown in FIGS. 2A and 2B, a tail extension 30 is disclosed forattachment to the ground return electrode unit 16 (shown in FIGS. 1A and1B) to extend the electrical termination of the ground return electrode14 (shown in FIGS. 1A and 1B), for example, further into the vitreouscavity. Further extension of the ground electrode into the vitreouscavity may be required to diminish undesirable skewing of the electricfield that travels from the stimulating towards the ground electrode.Such a skewed electric field is less efficient in stimulating theneuroretina compared to an electrical field that is arranged in adirection perpendicular to the neuroretinal surface.

FIG. 2A is a plan view and FIG. 2B is a side view of the tail extension30. The tail extension attachment 30 is constructed of a biocompatiblematerial 31, such as parylene or a similar biocompatible material and ispreferably manufactured with a curve. The tail extension attachment 30also includes an embedded conductor 34, insulated by the surroundingmaterial 31, terminating in a tail extension ground return electrode 32at or near an end of the tail extension attachment 30, preferably tolocate the electrode as far into the vitreous cavity as possible. Theconductor 34 of the tail extension attachment 30 is designed toelectrically contact the ground return electrode 14 when the tailextension attachment 30 is attached to the ground return electrode unit16 (shown in FIGS. 1A and 1B). The tail extension ground electrode 32 ispreferably constructed of iridium/iridium oxide, or other suitableelectrode material.

Also referring to FIGS. 1A and 1B, the tail extension attachment 30 hasa pocket 36 that fits over the ground electrode unit 16 to establishelectrical contact with the ground return electrode 14. Inside thepocket 36 are protrusions 38, which fit into the notches 26 of theground return electrode unit 16. The protrusions 38 are preferablyconstructed of a biocompatible material, such as parylene, or a similarbiocompatible material. The tail extension attachment 30 includes a slot40 that allows the positioning hole 24 of the ground return electrodeunit 16 to be access by an instrument (not shown).

FIG. 3 is a perspective view showing the tail extension 30 (shown inFIGS. 2A and 2B) electrically attached with the ground return electrodeunit 16 of the retinal device 10. The conductor 34 of the tail extension30 contacts the ground return electrode 14 of the ground returnelectrode unit 16. The tail extension 30 is preferably curved toposition its ground return electrode 32 into the vitreous cavity of theeye. Those skilled in the art will appreciate that other shapes of thetail extension could be used as long as the shape positions the groundreturn electrode into the vitreous of the eye. The stimulating electrodeunit 12 is also shown.

FIG. 4 is a perspective view of another embodiment of the retinal device10 shown in FIGS. 1A and 1B. Like components are labeled using the samereference numerals followed by a letter. Alternative embodiment retinaldevice 10 a is similar to the preferred embodiment retinal device 10shown in FIGS. 1A and 1B, except that the stimulating electrode unit 12a is fabricated as a disk-shaped web 17 to allow nourishment to flowbetween the choroid and the neuroretina, and the stimulating electrodesubunits 22 a are fabricated at the intersecting nodes of the web 17.Preferably, the web is manufactured of silicon and can be perforated.The alternative embodiment retinal device 10 a is thus similar to thepreferred embodiment retinal device 10 with the addition of fabricatednutrient openings 13.

FIG. 4A is a magnified plan view, and FIG. 4B is sectional view takenthrough section III-III of FIG. 4A of an alternative embodiment of theretinal device 10 a shown in FIG. 4. The stimulating electrode subunits22 a of the stimulating electrode unit 12 a shown in FIG. 4 are eachcomprised of first, second, and third microphotodiodes 24, 25, 26electrically connected, for example, in series within stimulatingelectrode subunit 22 a to increase the output voltage of eachstimulating electrode subunit 22 a. The stimulating electrode subunits22 a contact a common ground conductor 28 d via a contact pad 28 c.

Preferably the common ground conductor 28 d and contact pad 28 c areinsulated during fabrication, for example, by silicon dioxide 29deposition. For clarity purposes, preferably only the layers of one ofthe microphotodiodes connected electrically in series is labeled; theyare the n+ layer 24 a, the n type silicon substrate 24 b, the intrinsiclayer 24 c, and the p+ layer 24 d. Conductors 27 b, 28 b are preferablydeposited over insulating layers of silicon dioxide 27 a, 28 a toelectrically connect the adjacent microphotodiodes 24, 25, 26. Aninsulating layer of silicon dioxide 27 c covers conductor 27 b. Thestimulating electrode 27 of each stimulating electrode subunit 22 a ispreferably fabricated from iridium/iridium oxide deposited over atitanium adhesion layer. Those skilled in the art will appreciate thatother electrode materials, for example, noble metals like platinum andtantalium, may be used. The common ground conductor 28 d of thestimulating electrode subunits 22 a terminates electrically, forexample, at or near the ground return electrode 14 a of the groundreturn electrode unit 16 a, shown in FIG. 4.

FIG. 5 is a cross-sectional view showing the preferred embodimentretinal device 10 of FIGS. 1A and 1B implanted in the eye 6 with thestimulating electrode unit 12 disposed in the subretinal space betweenthe neuroretina 50 and the retinal pigment epithelium 52, and the groundreturn electrode unit 16 in the vitreous cavity 54. Light images 56enter the eye 6 through the cornea 58 and lens 60 and are focused ontothe stimulating electrode unit 12. Patterned electrical stimuli are thengenerated by the microphotodiodes of the electrode subunits 22 (FIG. 1A)that stimulate the overlying neuroretina 50 in the pattern of the image.For purposes of reference, other structures of the eye 6 that are shownare an iris 62, a sclera 64 and an optic nerve 66.

FIG. 6 shows a cross-sectional view of an alternate embodiment retinaldevice 10 b, including the preferred embodiment retinal device 10 asdescribed in FIGS. 1A and 1B and other features. The alternateembodiment retinal device 10 b includes the stimulating electrode unit12 disposed in the subretinal space between the neuroretina 50 and theretinal pigment epithelium 52, and the ground return electrode unit 16in the vitreous cavity 54, with attached tail extension 30 of FIGS. 2Aand 2B. A purpose of the tail extension 30 is to electrically extend thelocation of the ground return electrode further into the vitreous cavity54 to prevent skewing of the transretinal electric field between thestimulating electrode unit 12 and the ground return electrode unit 16 asthe electric field traverses through the neuroretina 50. A non-skewedelectrical field that is perpendicular to the neuroretinavitreous-facing surface efficiently stimulates remaining neuroretinalcells. For reference purposes, other items and structures of the eyethat are shown are the cornea 58, iris 62, lens 60, sclera 64, opticnerve 66 and the incident light images 56.

FIG. 7 shows a cross-sectional view of another embodiment of the retinaldevice 10 c including the preferred embodiment retinal device 10 asdescribed in FIGS. 1A and 1B and other features. The stimulatingelectrode unit 12 is disposed in the subretinal space between theneuroretina 50 and the retinal pigment epithelium 52, and the groundreturn electrode unit 16 is disposed in the vitreous cavity 54,including a tail extension 30 a that has a generally looped groundelectrode. Although the stimulating electrode unit 12 is preferablypositioned in the subretinal space with the ground return electrode unit16 positioned in the vitreous cavity, in other embodiments thepositioning of the stimulating electrode unit 12 and ground electrodeunit 16 may be reversed.

A purpose of the loop electrode of the tail extension 30 a is toelectrically extend the location of the ground return electrode furtherinto the vitreous cavity 54 and in an even manner. An evenly disposedground electrode in the vitreous cavity relative to the subretinalstimulating electrode array aids the maintenance of a transretinalstimulating electrical field in a perpendicular direction relative tothe neuroretinal surface. Such an alignment of the electrical fieldrelative to the neuroretinal surface efficiently stimulates theneuroretina, as compared to, for example, a transretinal electricalfield that is skewed to the neuroretinal surface. For purposes ofreference, other items and structures of the eye that are shown are thecornea 58, iris 62, lens 60, sclera 64, optic nerve 66 and the incidentlight images 56.

FIG. 8 shows a cross-sectional view of yet another embodiment retinaldevice 10 d including the preferred embodiment retinal device 10 asdescribed in FIGS. 1A and 1B, including an attached tail extension 30 b.The tail extension electrically connects with at least one biasphotodiode 30 c disposed in the lens capsule 60 b of the eye 6, the biasphotodiode 30 c containing the extended location of the ground returnelectrode 32B. The bias photodiode 30 c provides additional voltageand/or current to the electrode stimulating unit 12 in the subretinalspace. Additional stimulating voltage and the resulting current may berequired to stimulate more severely damaged retinas compared to lessseverely damage retinas. The bias photodiode, which may also be a seriesof photodiodes 30 c are electrically connected together in a series orparallel configuration, as is known in the art, to provide the increasedvoltage and/or current. For purposes of reference, other items andstructures of the eye 6 that are shown are the cornea 58, iris 62,sclera 64, neuroretina 50, retinal pigment epithelium 52, optic nerve66, and the incident light images 56.

FIG. 9 shows a cross-sectional view of yet another embodiment retinaldevice 10 e including the preferred embodiment retinal device 10 asdescribed in FIGS. 1A and 1B, and an attached tail extension 30 d thatelectrically connects with at least one bias photodiode 30 e preferablydisposed in front of the iris 62 of the eye 6. The placement of at leastone bias photodiode in this location allows all of the bias photodiodeto be exposed to light, compared to a bias photodiode disposed behindthe iris. The bias photodiode 30 e contains the extended location of theground return electrode 32 c, and the bias photodiode or photodiodes 30e to provide additional voltage and/or current to the electrodestimulating unit 12 in the subretinal space. The bias photodiode orphotodiodes 30 e are electrically connected together in a series orparallel configuration to provide increased voltage and/or current, asis known in the art. For reference purposes, other items and structuresof the eye 6 that are shown are the cornea 58, lens 60, sclera 64,neuroretina 50, retinal pigment epithelium 52 and optic nerve 66, andthe incident light images 56.

It is to be understood that changes and modifications to the embodimentsdescribed above will be apparent to those skilled in the art, and arecontemplated. It is therefore intended that the foregoing detaileddescription be regarded as illustrative rather than limiting, and thatit be understood that it is the following claims, including allequivalents, that are intended to define the spirit and scope of thisinvention.

1. An artificial retina device to electrically stimulate a neuroretinaof an eye to produce artificial vision, the artificial retina devicecomprising: an electrical source; at least one stimulating electrodeconnected with the electrical source; and at least one ground returnelectrode connected with the electrical source.